Method of determining the volume of a lower uncased portion of a well



METHOD OF DETERMINING THE VOLUME OF A LOWE UNCASED PORTION OF A WELL Filed Aug. 16, 1937 March 18,1941 MCCQNNE-LL R 2,235,776

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A TTOIRNEK Patented 18, 1941 PATENT omen Mn'rnon or DETERMINING 'rns vowm:

or A rowan mvcssnn roa'noN or A Fred I. McConnell, Midland, Tex. alsignor to The Dow Chemical company, mdla'nd, Mioh.,-a corporation oi Michigan Application August 16, 1937, Serial No. 15am 6 Claims.

The invention relates to a method of determining the volume of a lower uncased portion oi. a deep well.

The lower uncased portion of a well, such as an oil or gas well, usually has an irregular shape,

which may be due to shooting, sloughing oif,

caving or other causes. In some 01 the operations employed to facilitate production of wells,

such as acidizing and the like, wherein a known 10 volume of a liquid reagent is introduced into the well, it is desirable and sometimes necessary to know quite accurately the volume of the uncased portion of the bore hole in order to control the level to which the treating agents may rise in the well. For example, a well traversing a pro ductive stratum and ending in a non-productive porous stratum could be more efliciently acidized,

if all the acid were directed into the producing stratum. By measuring the volume of the portion of the hole below the producing stratum, the

proper volume of a temporary or permanent plugging material can be ascertained, which will just fill this portion of the well. After filling this 'portion of the well bore with the plugging material, acidization can be conducted without waste of acid in the non-productive' stratum.

It is therefore the principal object of the invention to provide a method whereby the volume of a lower uncased portion of a well can be easily and accurately measured.

Another object is to provide a material which may be used in the measurement of the volume of a lower uncased portion of a well, which will not penetrate into porous formations, yet will be easily removable from the well bore.

Still other objects and advantages of the invention will be apparent from the following description.

I have now found that the volume of the lower uncased portion of the well bore can be easily and accurately measured by locating the lower end of the tubing at the level below which it is desired to measure the volume of the bore hole, introducing into the bottom of the well a blown amount 4 v of a non-penetrating liquid mixture, the amount being in excess of that required to fill the bore hole to the level of the bottom of the tubing, and then removing from the well through the tubing the excess of the liquid mixture standing above 50 the level of the lower end of the tubing.

The term non-penetrating liquid mixture as used herein and in the appended claims means a liquid mixture comprising a dispersion or suspension in a liquid of a material which prevents the 55. liquid from penetrating porous formations, such as those traversed by a well bore, but of sufilcientfluidity to be introduced into the well and readily withdrawn therefrom.

The accompanying drawing forming a part of this specification, and which illustrates a mode 5 of carrying out the invention, is a diagrammatic view in vertical section of a gas well. I

The single figure isv a view showing the well equipped for carrying out a measurement of the volume of the uncased portion of the bore hole -10 according to the invention.

In the drawing the upper portion I of the well is cased and passes through the non-productive earth and rock, the lower portion of the casing 2 being cemented in rock stratum 3 at casing seat 4, 1 while its lower portion ends in the uncased well bore 5, located in the producing stratum 6, above an impervious stratum l. The uncased well bore 5 is shown filled with the non-penetrating liquid mixture 8 to a level 9, above the level of the 20 lower end of the tubing ill. The uncased well bore 5 is alsoshown with the excess nonpenetrating liquid mixture 8 removed from the well, the level of said mixture 8 then being at the lower end of tubing it or at the casing seat 4. Above 2 the ground level the casing head 2i, through which the tubing it extends into the well, is shown equipped with pipes ii and i2 communicating with the casing, said pipes being provided with valves l3 and it. To the tubing ill above 30 the casing head pipes IE, it, and i9, controlled by valves til, it, and- 20, respectively, are connected, suitably arranged for producing the well and for carrying out the method according to the invention.

According to my invention, I carry out a measurement of the volume of the uncased portion of the bore hole, such as the volume below the casing seat i, in the following manner. The well tubing it is lowered until its lower end is at a 40 point opposite the casing seat 6. A measured quantity of a non-penetrating liquid mixture is then introduced into the well through the tubing ill, while maintaining a pressure on the well greater than the bottom hole pressure, a suflicient quantity of the liquid being introduced to fill the well to a level 9, for example, above the lower end of the tubing it. Such an amount is readily ascertained with suflicient accuracy for the purpose from a knowledge of the depth of the bore hole below the casing seat 3 and the condition of the well. A considerable excess of the liquid mixture over that amount required to fill the space to b measured is employed, to insure that the non-penetrating liquid completely fills the 'ture.

2 uncased portion of the hole below the casing seat 4 and rises above the level at which the lower end of the tubing III has been placed. The excess non-penetrating liquid mixture not required to fill the bore hole below the level of the lower end of the tubing is then removed from the well in any suitable manner. For example, by forcing into the casing a liquid slightly lighter than, and immiscible with the non-penetrating liquid mixture in the bore, while still maintaining a pressure on the well greater than that of the bottom hole pressure, the quantity of the excess liquid mixture standing above the level of the lower end of the tubing is forced out of the well through the tubing and measured, leaving the uncased portion of the bore below the casing seat completely filled with the non-penetrating liquid mix- The actual volume of the uncased portion of the bore hole is obtained by deducting the volume of the excess discharged from the well from the volume of the non-penetrating liquid mixture first introduced into the well. After the determination of the volume, the non-penetrating liquid mixture remaining in the well is removed by lowering the tubing to the bottom of the bore and applying gas or liquid pressure to the casing so as to force said liquid out of the wellthrough the tubing.

The above described method as applied to a to force the liquid in the hole into the porous formation by applying pressure on the non-penetrating fiuid. Adjustment of the specific gravity of the non-penetratingliquid mixture may also be made, so that it will displace the liquids in the v hole. Other methods of introducing and removing the non-penetrating liquid mixture may be employed, if desired. For instance, the liquid mixture may be introduced by allowing it to drop through the casing or tubing and removed by pumping it up through the tubing.

Also, a measurement of the volume of a specific portion of the lower uncased bore hole may be made by first measuring according to the described method the volume of the well bore up to the lower level of the portion it is desired to measure, allowing the non-penetrating liquid mixture filling the well bore up to the level of the portion to be measured to remain in the hole, while carrying out another measurement of the specific portion by raising the tubing to the top level of said portion and obtaining the volume between the two levels according to the described method.

I have found that suitable non-penetrating liquid mixtures for my purpose consist of aqueous mixing between about 0.1 and 8.0 per cent, and

preferably about 1.5 to 4.0 per cent, of such an organic jellifying material with water, a nonpenetrating liquid is obtained which will readily fiow, or can be pumped. Such a mixture will also withstand high pressures without penetrating porous formations. Tests on porous cores taken from typical formations have shown that pressures of several thousand pounds per square inch on such a mixture cause little or no penetration of the liquid mixture into the interstices of the cores. A suitable material of this nature, having non-penetrating characteristics when mixed with water, can be prepared from starches such as those of cassava or rice by mixing them with water to form a thin paste, and boiling the mixture until the starch is hydrolyzed. The cooked starch is dried at about C. and the dried material ground, preferably to a fine powder. The powder so produced, when mixed with water in a concentration of from 1-8 per cent by weight, readily forms a substantially non-penetrating liquid mixture.

Other liquid mixtures may be used for my purpose providing they will not penetrate porous foramtions at relatively high pressures, and can be made to fiow readily through conventional well equipment. In many cases it may be desirable to weight or increase the specific gravity of some of the nonpenerating fluid mixtures. By adding suitable weighting agents consisting of a soluble salt, such as calcium chloride, zinc chloride, etc., a fiuid mixture may be obtained having the desired specific gravity. In general I prefer to employ a fiuid mixture that will not adhere readily to the metal equipment of the well, such as the tubing, to avoid a volume loss during the measurement.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

I therefore particularly point out and distinct- 1y claim as my invention:

l. In a method of measuring the volume of a lower uncased portion of a well provided with the usual casing and tubing, the steps which comprise introducing into the well a known volume of a substantially non-penetrating liquid mixture in excess of that required to fill the well up to the lower end of the tubing, and then removing from the well through the tubing the portion of the liquid mixture occupying the space in the well above the lower end of the tubing, measuring the volume of the liquid so removed, and deducting said volume from the volume of the non-penetrating liquid mixture first introduced into the well, whereby the volume of the well bore below the lower end of the tubing is obtained.

2. In a method of measuring a volume of a lower uncased portion of a well provided with the usual casing and tubing, the steps which comprise introducing into the well a known volume of an aqueous dispersion of an organic jellifying material in excess of that required to fill the well up to the lower end of the tubing, removing from the well through the tubing the portion of the aqueous dispersion of the organic jellifying material occupying the space in the well above the lower end of the tubing, measuring the volume of the liquid so removed, and deducting said volume from the volume of the non-penetrating liquid mixture first introduced into the well, whereby the volume of the well bore below the lower end of the tubing is obtained. g

3. In a method of measuring the volume of a. lower uncased portion of a well provided with the usual casing and tubing and having liquid standing in the well bore, the steps which comprise introducing into the well a known volume of a substantially non-penetrating liquid mixture of a greater specific gravity than that of the liquid standing in the well bore and in amount in excess 01' that required to fill the well up to the lower end of the tubing, and then removing from the well through the tubing the portion of the liquid mixture occupying the space in the well above the lower end of the tubing, measuring the volume of the liquid so removed, and deducting said volume from the volume. of the nonpenetrating liquid mixture first introduced into the well, whereby the volume of the well bore below the'lower end of the tubing is obtained.

4. In a method of measuring t e volume of a lower uncased portion ofa well provided with the usual casing and tubing, the steps which comprise removing liquid standing in the well bore, introducing into the well a known volume of a substantially non-penetrating liquid mixture in amount in excess of that required to fill the bore hole up to the lower end of the tubing, and removing from the well through the tubin the portion of the non-penetrating liquid mixture occupying the space in the well above the lower end of the tubing, measuring the volume of the liquid so removed, and deducting said volume from the volume or the non-penetrating liquid mixture first introduced into the well, whereby the volume of the well here below the lower end of the tubing is obtained.

5. In a method of measuring the volume of a lower uncased portion of a wellcontaining liquid,

said well being provided with the usual casing and tubing, the steps which comprise forcing the liquid standing in the well out into the formation by applying pressure in excess of the bottom hole pressure on a. known volume of a substantially non-penetrating liquid mixture of a. lower specific gravity than that of the liquid standing in the hole, introduced into the well in amount in "excess of that required to fill the well up to the lower end of the tubing, and then removing from the well through the tubing the portion of the liquid mixture occupying the space in the well above the lower end of. the tubing, measuring the volume of the liquid so removed, and deducting said volume from the volume of the non-penetrating liquid mixture first introduced into the well, whereby the volume of the well bore below the lower end of the tubing is obv tained.

6. In a method of measuring the volumeof a lower uncased portion of a well provided with the usual casing and tubing, the steps which comprise lowering the tubing to a point below which it is desired to measure the volume of the uncased portion, introducing into the well a. known volume of a substantially non-penetrating liquid mixture in excess of that required to 'fill the encasedportion of the well up to the lower end of the tubing, and then removing from the well through the tubing the portion of the liquid mixture occupying .the space in the well above the lower end of the tubing, measuring the volume of the liquid so removed, and deducting said volume from the volume of the non-penetrating liquid mixture first introduced into the well, whereby the volume of the well bore below the lower end of the tubing is obtained.

FRED I. McCONNELL. 

